Under certain circumstances, if the flow through a gas turbine compressor separates over the airfoils sufficiently, the airfoil stalls, and the airfoil loses the ability to pump gas through the engine. The high pressure gas downstream, i.e. from the combustor and turbine sections of the engine, flows forward to the lower pressure stages of the engine. This “surge” lasts for 10-50 milliseconds. The surge condition may disappear and return some milliseconds later, creating a vibration which puts extreme load on the engine blades and shaft. This condition is not desirable and therefore various techniques have been developed for addressing surge in a gas turbine engine. To be able to address surge requires that surge conditions be detected.
Accordingly, there is a need to provide a method and apparatus for detecting a surge condition during the operation of gas turbine engines.